Would have sworn this was photoshop but it is actually not a mutation but an apparent case of tetragametic chimerism a different theory than the one Zahdia poses. This link suggests two fraternal/non-identical zygotes fuse, so there's one individual made up of the tissues/DNA of both. Apparently this has happened to humans as well, where a mother, for instance, has DNA that does not match her ...

He's adorable!!
Random fact: The bridge of the nose is how you tell their genders apart. Blue is a male, pink is female. It can be hard to tell sexes apart in the first year before the color really sets in.

I had a blue and green budgie when I was a kid I would play with them everyday, they liked me so much they would fly on my hand and give me kisses. We would sometimes put their cage outside so they could get air but of course leave the cage locked. One day we all went to the beach and left them outside, when we got back the door was open and they were gone. I spent hours looking around the forest ...

Ah genetics. Genetic mosaic perhaps? Although the bird has the same genes, early in embryo development each cell made a choice: green allele or blue. Once decided all progeny daughter cells had to be that color. I'm sure this isn't what happened, as this is simplified and genetic event are much more complex. But this genetic mosaic is the reason female calico cats look as they do. But this ...

I really hope that you were at the pet store with a friend/parent/whatever, and that it was standing still and the two of you approached it from opposite sides. Then one of you was like "Oooo, look at the pretty blue one" "what blue one? you mean the green one?" "No, the blue on standing near the top of the cage, it's so majestic" "Which bird are you talking about, there is no blue one" "What do ...